Hydrocarbon drilling systems utilize drilling fluid or mud for drilling a wellbore in a subterranean earthen formation. Specifically, in some applications drilling fluid is pumped through a passage in a drill string extending into the wellbore, and down to a drill bit connected to a lower end of the drill string. The drilling fluid is ejected from the drill string through ports in the drill bit where the drilling fluid is used to cool the drill bit and transport materials cut from the wellbore to the surface via an annulus disposed between an inner surface of the wellbore and an outer surface of the drill string. Upon reaching the surface, the drilling fluid is flowed through a mud return line and deposited in a mud tank for processing prior to being flowed back into the drill string. In some applications, accurately measuring the level of drilling fluid flow through the mud return line is important for monitoring the drilling fluid balance in the wellbore. Several different types of sensors are used for measuring the flow rate of drilling fluid through the mud return line, including paddle flowmeters featuring a mechanical paddle that rises and falls with the level of drilling fluid in the mud return line, and non-contact radar level sensors that transmit a radar pulse that is reflected off of a surface of the drilling fluid flowing in the mud return line to determine the amount of fluid flowing through the mud return line.